Add polling Docker deployments

Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

server/poll-deploy.sh

@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+repository="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+expected_repository="$HOME/yawn"
+state_directory="$HOME/.local/state/yawn"
+deployed_revision_file="$state_directory/deployed-revision"
+compose=(docker compose --project-name yawn --project-directory "$repository" --file "$repository/compose.yaml")
+
+if [[ "$repository" != "$expected_repository" ]]; then
+    printf 'Expected the repository at %s, found %s\n' "$expected_repository" "$repository" >&2
+    exit 1
+fi
+
+for command in git docker flock; do
+    if ! command -v "$command" >/dev/null 2>&1; then
+        printf 'Missing required command: %s\n' "$command" >&2
+        exit 1
+    fi
+done
+if ! docker compose version >/dev/null 2>&1; then
+    printf 'Docker Compose v2 is required.\n' >&2
+    exit 1
+fi
+
+mkdir -p "$state_directory"
+exec 9>"$state_directory/deploy.lock"
+if ! flock -n 9; then
+    printf 'Another Yawn deployment is already running.\n'
+    exit 0
+fi
+
+cd "$repository"
+if [[ "$(git branch --show-current)" != "main" ]]; then
+    printf 'Deployments must run from the main branch.\n' >&2
+    exit 1
+fi
+if [[ -n "$(git status --porcelain --untracked-files=normal)" ]]; then
+    printf 'Refusing to deploy a checkout with local changes.\n' >&2
+    exit 1
+fi
+
+git fetch origin main
+remote_revision="$(git rev-parse FETCH_HEAD)"
+current_revision="$(git rev-parse HEAD)"
+deployed_revision=""
+if [[ -f "$deployed_revision_file" ]]; then
+    read -r deployed_revision <"$deployed_revision_file"
+fi
+
+container="$("${compose[@]}" ps -q yawn 2>/dev/null || true)"
+container_status="missing"
+if [[ -n "$container" ]]; then
+    container_status="$(docker inspect --format '{{if .State.Health}}{{.State.Health.Status}}{{else}}{{.State.Status}}{{end}}' "$container" 2>/dev/null || true)"
+fi
+
+if [[ "$current_revision" == "$remote_revision" &&
+    "$deployed_revision" == "$remote_revision" &&
+    "$container_status" == "healthy" ]]; then
+    printf 'Yawn is already running revision %s.\n' "${remote_revision:0:12}"
+    exit 0
+fi
+
+printf 'Deploying revision %s...\n' "${remote_revision:0:12}"
+flock -u 9
+exec 9>&-
+"$repository/server/deploy-docker.sh"